Given the task definition and input, reply with output. Based on the information present in the given passage, you need to write a correct answer to the given question. A correct answer is one that correctly and completely answers the question. Do not write answers that address the question partially or incorrectly. The correct answer must be contained in the given paragraph.

Paragraph- Sent 1: An atom is the very smallest particle that still the elements properties.
Sent 2: All the atoms of an element are alike.
Sent 3: They are also different from the atoms of all other elements.
Sent 4: For example, atoms of gold are always the same.
Sent 5: It does not matter if they are found in a gold nugget or a gold ring.
Sent 6: All gold atoms have the same structure and properties.
Sent 7: For example, all gold atoms contain 79 protons.
Sent 8: One of golds unique properties is that it is a great conductor of electricity.
Sent 9: Gold is a better conductor of electricity than copper.
Sent 10: Gold is more rare and expensive than copper.
Sent 11: Copper is used in house wiring.
Sent 12: Gold is far too expensive. 
Question: What is used in house wiring and why?.

Copper is used in house wiring because gold is far too expensive.